Human visual event-related potentials (ERPs) measure a variety of different cognitive operations during visual processing. Visual ERPs are invaluable in diagnosing and studying neurological and psychopathological disorders in addition to revealing how the health brain turns visual inputs into appropriate responses. However, it has proven very difficult to definitively determine what brain areas generate specific ERP components related to deploying visual attention and monitoring task performance. We propose to directly locate the sources of ERP components elicited during visual processing and task performance using both humans and nonhuman primates. In the latter we will record noninvasive ERPs simultaneously with intracranial recordings of local field potentials. Preliminary evidence from monkeys and humans performing identical visual tasks demonstrates homology between human and macaque ERP components indexing visual attentional deployment and performance monitoring. By concurrently studying humans and monkeys this project will allow clinicians and health researchers to use the visually and response evoked ERP components recorded noninvasively from humans to access whether specific brain regions are functioning properly and also to develop animal models of specific disorders.